Difference between Rigidity and Fluidity of Matter

We know that matter may change form since it is made up of microscopic particles. But what are the properties of these matter particles? What exactly is the science behind it? Let’s learn more about them down below. The matter is defined as everything that has mass and takes up space. Different types of matter include pens, paper, clips, land, air, ice, and so on. Every substance is made up of microscopic particles. These particles are so small that they are invisible to the human eye. Let’s look at the many properties of matter particles.

Characteristics of Particles of Matter 

The following are the properties of matter particles: 

• All matter is made up of extremely tiny particles that may exist independently: A matter is made up of very tiny particles which may be atoms or molecules, for example- when we dissolve a spoon of salt or sugar in a glass of water.
• Spaces exist between matter particles: The particles of matter are very small beyond imagination these particles have space between them.
• Matter particles are always moving: This is because of the kinetic energy possessed by the particles which increases on increasing the temperature and so particles move much faster.
• Matter particles are attracted to one another: The attractive forces bind the particles of matter in a single body and also lead to the arrangement of particles. The particles of matter have a force acting between them.

Rigid Matter

Rigid matter can also be called Solid matter. In Solid, the particles are very closely packed. And, thus the force of attraction between particles is very strong. 

Due to its closely packed nature, it has a definite shape and volume. The solids have a high density and can not be diffused.  

e.g. A rubber band is a solid because it can change its shape under force and regain its shape when force is removed if excessive force is applied it breaks. This is an exceptional case of the solid.

Properties of Rigid Matter are:

• Definite shape, size, volume, and distinct boundaries.
• Negligible compressibility.
• Solids have a tendency to maintain their shape when subjected to outside force.
• They are rigid, difficult to change their shape.
• Mass per unit volume of a substance is called density.
• Intermolecular force is high in solids.
• Kinetic energy is very low in solids.
• Solids do not possess the property of diffusion.

Fluid Matter

Liquid matter can also be called as Liquid matter. In Liquids, the particles are less closely packed as compared to solid. And, thus Force of attraction between particles is also less strong. 

They do not have a definite shape but have a definite volume. Also, Density is lower than solids and can diffuse.

Properties of Fluid Matter are:

• Do not have a definite shape or distinct boundaries but have a fixed volume.
• They can be compressed.
• In Science the common name of gases and liquids is fluid.
• Liquids are not Rigid but have the property of flowing that’s why liquids are called fluids.
• Intermolecular force is less than the solids.
• In liquid kinetic energy is more than solid.
• Liquid has moderate density.
• Liquids possess the property of diffusion.
• They can take any shape.
• The gases Oxygen and Carbon dioxide from the atmosphere diffuse and dissolve in water. Due to these gases, aquatic plants and animals are able to survive.
• Diffusion is much more in liquid than in solid due to the free movement of particles of liquid.

Difference between Rigidity and Fluidity 

Lets now understand some key differences between Rigidity and Fluidity as,

	Rigidity	Fluidity
1.	Rigidity is the ability of a solid to maintain its form as it changes. That is, when an external force is applied to a solid substance, the form will remain unchanged.	Fluidity is a characteristic that allows a molecule’s particles to move around in space. Fluidity refers to the ease with which particles may move about in a material.
2.	It is the strongest force of attraction between particles and this property makes the solid rigid.	Fluidity cannot resist a shear force or stress without moving as can a solid. Therefore, a lesser force of attraction and more space between particles makes the liquid and gas flow easily.
3.	It is usually classified as Solids.	It is usually classified as liquids or gases.
4.	Rigidity gives the perfect shape to solids, as the particles in the solid are tightly packed.	Fluidity does not give the perfect shape to solids, as the particles in the liquid or gas are loosely packed.
5.	Thus, the matters which exhibit such property are called Rigid matters. e.g. Solids.	Thus, the matters which exhibit such property are called Fluid matters. e.g. Liquid and gas.

Sample Questions

Question 1: What do you mean by “Rigidity”?

Answer:

The tendency of a substance to retain/maintain their shape when subjected to outside force is called Rigidity.

Question 2: What is the physical state of water at (a) 250°C (b) 100°C.

Answer:

(a) Physical state of water at 250°C is a gaseous state because the boiling point of water is 100°C. Therefore at a temperature higher than its boiling point, it exists as gas.

(b) At 100°C both liquid and gaseous states are present. These are in a state of equilibrium. So at 100°C both liquid water and vapours are present.

Problem 3: What produces more severe bums, boiling water or steam?

Answer:

Steam at 100°C will produce more severe bums as extra heat is hidden in it called latent heat whereas the boiling water does not have this hidden heat.

Question 4: Why does our palm feel cold when we put some acetone or petrol or perfume on it?

Answer:

Both acetone and perfume are low boiling liquids. When they are poured on the palm, they evaporate readily and for this change of state they take the energy from the palm and we get a cooling sensation.

Question 5: What is the reason behind Naphthalene balls disappear with time without leaving any solid.?

Answer:

Naphthalene balls disappear with time without leaving any solid because they undergo sublimation i.e they directly change into vapours without passing through the liquid state.